Piston pin assembly

ABSTRACT

A method for reducing the incidence of piston pin failure by providing a retainer assembly for piston pin plugs such that the plugs cannot be removed or shaken lose during operation. A plastic rod is inserted into the piston pin, and the rod is ultrasonically welded to the stems of mushroom-shaped plastic piston plugs such that the plugs cover the open ends of the pin and are held in place by the cooperation of structure between the plugs and the rod. In an alternate embodiment, the stem of each pin plug is hollow and a respective internally threaded brass insert is disposed in the stem and ultrasonically welded therein. An externally threaded rod is then engaged with the two internally threaded inserts to hold the plugs on the piston pin.

TECHNICAL FIELD

[0001] The present invention relates generally to vehicle engines, andmore particularly to piston pins.

BACKGROUND ART

[0002] In internal combustion engines, the bottom ends of the pistonrods are coupled to a crankshaft and the top ends are coupled torespective piston crowns such that linear reciprocating motion of thepiston crowns is converted to rotational motion of the crankshaft.Accordingly, the top ends of the rods must be coupled to the pistoncrowns, which move in only a single degree of freedom, in such a waythat permits the bottom ends of the rods to move in two degrees offreedom.

[0003] The key mechanism in coupling a piston rod to a piston crown isthe piston pin, which passes through a piston skirt and piston crown andcontinues on through the piston rod. By means of the piston pin, thepiston crown and the piston rod are firmly joined together. It will bereadily appreciated that the failure of a piston pin could result inmisalignment and/or separation of these components, which could causesevere engine damage.

[0004] It happens that piston pins ordinarily are held with metal clips,which can fail. Accordingly, as recognized herein, it is desirable toprovide a means for holding the piston pins in engagement with thepiston rod. The present invention further understands that this can beaccomplished using piston plugs that are inserted into the pins, butthat it is possible for the plugs to shake loose from the pins duringoperation, thereby potentially causing damage to the engine. The presentinvention understands that simply gluing the plugs to the pins would beless than effective, because the adhesive could potentially lose itseffectiveness in the harsh engine environment. Accordingly, the presentinvention provides the solutions disclosed herein to retain plasticpiston plugs in piston pins.

DISCLOSURE OF THE INVENTION

[0005] A piston pin assembly includes a hollow piston pin defining firstand second ends. A first pin plug is disposed in the first end and asecond pin plug is disposed in the second end. A rod interconnects theplugs.

[0006] In a preferred embodiment, each pin plug includes a head disposedoutside the piston pin and a stem disposed within the pin. In a firstembodiment, the stem of each pin plug can be solid, and both the stemsof the pin plugs and the rod are made of plastic. In this firstembodiment, the stems are ultrasonically welded to the rod.

[0007] In a second preferred embodiment, the stem of each pin plug ishollow and the rod is externally threaded. A respective internallythreaded brass insert is disposed in each stem for threadably engagingthe rod. To permit rotating the head of at least one of the plugs bymanipulating a tool, the head is formed with at least one engagementsurface configured for engaging the tool. The engagement surface can beestablished by at least one notch.

[0008] In another aspect, a piston pin plug retainer assembly includes arod disposable in a hollow piston pin having opposed open ends, andfirst and second plastic plugs affixed to opposite ends of the rod tocover the open ends of the piston pin.

[0009] In still another aspect, a method for retaining first and secondplastic pin plugs in first and second ends of a piston pin includescoupling the first plug to a rod, and advancing the rod into the pistonpin. The second plug is coupled to the rod. If desired, both plugs canbe coupled to the rod after the rod is advanced into the pin.

[0010] The details of the present invention, both as to its structureand operation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an exploded view of a piston assembly with the presentpiston pin plugs, with portions removed for clarity;

[0012]FIG. 2 is a cross-sectional view of the pin retainer assembly ofthe present invention; and

[0013]FIG. 3 is an exploded cross-sectional view of an alternate pistonpin retainer assembly.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Referring initially to FIG. 1, left and right piston pin plugs10, 12 engage open opposed ends of a piston pin 14 and are held in placeusing structures shown further below in reference to FIGS. 2 and 3. Thepiston pin 14 is received through brackets 16, 18 of a piston crown 20and through opposed openings 22 of a piston skirt 24. Also, the pistonpin 14 is received through a bearing 26 and a pin fitting 28 of a pistonrod 30. The piston rod 30 in turn is coupled to an engine crankshaft inaccordance with well-known principles. With this structure,reciprocating motion of the piston in a cylinder is transformed torotational motion of the crankshaft.

[0015] The details of the present pin retainer can be seen in referenceto FIG. 2, wherein a solid or hollow plastic piston pin rod 32,preferably made of polyethersulfone (PES) or other appropriate plastic,lies inside piston pin 14, with the plastic piston plugs 10 and 12sealing the ends of that piston pin. As shown, each plug 10, 12 ismushroom-shaped. Accordingly, taking the left plug 10 as an example, theleft plug 10 includes a preferably solid cylindrical stem 10 s and asolid dome-shaped head 10 t. If desired, however, the stem 10 s can behollow. Preferably, the plugs 10, 12 can also be made of PES.

[0016] The assembly shown in FIG. 2 is established by inserting the stem10 s of the piston plug 10 into the left end of the piston pin 14, asshown, and then advancing the plastic piston pin rod 32 into the rightend of the pin 14. The piston plug 10 and the piston pin rod 32 are thenfastened together, preferably by ultrasonically butt-welding themtogether as shown. Then, the stem of the right plug 12 is inserted intothe right end of the piston pin 14 and ultrasonically butt-welded to therod 32, thus forming a solidly welded single unit.

[0017] It is to be understood that the right plug 12 could be firstinserted into the pin 14, then the rod 32 advanced into the pin 14, andthen the left plug 10 advanced against the rod 32. Or, the rod 32 can bedisposed in the pin 14, and then both plugs 10, 12 welded to the rod 32.

[0018] Now referring to FIG. 3, an alternate piston pin retainer isshown, generally designated 120. In this alternate embodiment, left andright plastic pin plugs 122, 124 are provided that are in all essentialrespects identical to the plugs 10, 12 discussed above, with thefollowing exceptions.

[0019] The stems 126, 128 of the plugs 122, 124 are hollow, and arespective hollow cylindrical internally threaded insert 130, 132 isdisposed in each stem 126, 128. The inserts 130, 132 can be made ofbrass. If desired, the inserts 130, 132 can be ultrasonically welded tothe inside of the respective plug stem 126, 128.

[0020] As also shown in FIG. 3, a hollow or more preferably solidcylindrical externally threaded plastic or metal rod 134 is threadablyengaged with one of the inserts 130, 132 to couple the rod 134 to therespective plug 122, 124. The rod 134 is advanced into a piston pin suchas the pin 14 shown in FIGS. 1 and 2, and then the second insert 132,130 is threadably engaged with the rod 134 to couple the rod 134 to therespective plug 124, 122.

[0021] If desired, the head 136, 138 of each of the plugs 122, 124 canbe formed with an engagement surface that is configured for engaging atool to permit rotating the head 136, 138 by manipulating the tool. Inone preferred embodiment, the engagement surfaces can be established bynotches 140, 142 on the respective heads 136, 138 of the plugs 122, 124to provide a grip point to help tighten the assembly 120 together. Athread lock can be used to retain the integrity of the assembly.

INDUSTRIAL APPLICABILITY

[0022] In operation, either one of the plug retainer assembliesdescribed above are engaged with respective piston pins, after the pinshave been coupled to piston assemblies as set forth previously. Owing tothe above-disclosed combination of structure, the plug retainerassemblies hold the plugs 10, 12, 122, 124 into the respective pistonpins during engine operation.

[0023] While the particular piston pin assembly as herein shown anddescribed in detail is fully capable of attaining the above-describedobjects of the invention, it is to be understood that it is thepresently preferred embodiment of the present invention and is thusrepresentative of the subject matter which is broadly contemplated bythe present invention, that the scope of the present invention fullyencompasses other embodiments which may become obvious to those skilledin the art, and that the scope of the present invention is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more”.

What is claimed is:
 1. A piston pin assembly, comprising: a hollowpiston pin defining first and second ends; a first pin plug disposed inthe first end; a second pin plug disposed in the second end; and a rodinterconnecting the plugs.
 2. The assembly of claim 1, wherein each pinplug includes a head disposed outside the piston pin and a stem disposedwithin the pin.
 3. The assembly of claim 2, wherein the rod is solid orhollow.
 4. The assembly of claim 2, wherein the stem of each pin plug issolid or hollow.
 5. The assembly of claim 2, wherein the stems of thepin plugs and the rod are made of plastic.
 6. The assembly of claim 2,wherein the stems are ultrasonically welded to the rod.
 7. The assemblyof claim 2, wherein the stem of each pin plug is hollow and the rod isexternally threaded, and the assembly further comprises: a respectiveinternally threaded insert disposed in each stem for threadably engagingthe rod.
 8. The assembly of claim 7, wherein the inserts are made ofbrass.
 9. The assembly of claim 7, wherein the head of at least one pinplug is formed with at least one engagement surface configured forengaging a tool to permit rotating the head by manipulating the tool.10. The assembly of claim 9, wherein the engagement surface isestablished by at least one notch.
 11. A piston pin plug retainerassembly, comprising: a rod disposable in a hollow piston pin havingopposed open ends; and first and second plastic plugs affixed toopposite ends of the rod to cover the open ends of the piston pin. 12.The assembly of claim 11, wherein the stems are ultrasonically welded tothe rod.
 13. The assembly of claim 11, wherein the stem of each pin plugis hollow and the rod is externally threaded, and the assembly furthercomprises: a respective internally threaded insert disposed in each stemfor threadably engaging the rod.
 14. The assembly of claim 13, whereinthe head of at least one pin plug is formed with at least one engagementsurface configured for engaging a tool to permit rotating the head bymanipulating the tool.
 15. A method for retaining first and secondplastic pin plugs in first and second ends of a piston pin, comprisingthe acts of: coupling the first plug to a rod; advancing the rod intothe piston pin; and coupling the second plug to the rod.
 16. The methodof claim 15, wherein both plugs are coupled to the rod after the rod isadvanced into the pin.
 17. The method of claim 15, wherein the couplingacts include ultrasonic welding.
 18. The method of claim 17, wherein theplugs are butt welded to the rod.
 19. The method of claim 17, furthercomprising disposing a respective insert in each plug and ultrasonicallywelding the insert to the plug, the insert being configured for engagingthe rod.